End effector for substrate handling

ABSTRACT

An end effector has a tower with non-stacked spatulas. Tolerance stacking is avoided by making grooves in the tower relative to a common reference surface, and mounting the spatulas in such grooves. The grooves are provided in separate planar walls of the tower. The walls intersect to enhance the structural properties of the tower. The tower has a dual-purpose clamp formed integrally with one wall for use in assembling the tower and the spatulas, and for mounting the completed end effector in a load lock. The spatula may carry a wafer during various operations, e.g., semiconductor processing, material deposition and etching systems, or in flat panel display processing systems. The carrying of the wafers is notwithstanding vibration of equipment for performing the manufacturing operations, which vibration is primarily in a range of frequencies. Each spatula is formed with a planar platform having an aperture formed therein such that the platform carrying the wafer has a resonant frequency dimensioned so that the resonant frequency while carrying the wafer is outside of the range of frequencies of the equipment vibration. Holes are provided around the aperture, and the spatula is provided with a pad for assembly with each of the holes. Each of the pads has a wafer support surface and a plurality of legs depending from the support surface. The legs are flexed to permit reception of the pad in one of the holes. Methods are disclosed for making the tower, the spatulas, and the end effector with these features.

This application is a divisional of Ser. No. 09/107,917 filed Jun. 30,1998 U.S. Pat. No. 6,073,828.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to substrate handling, and moreparticularly, to towers for positioning substrates and to methods ofefficiently manufacturing the towers, components of such towers, and endeffectors using such towers and components.

2. Description of the Related Art

Transport chambers are generally used in conjunction with a variety ofsubstrate processing chambers, which may include semiconductorprocessing systems, material deposition systems, and flat panel displayprocessing systems. Growing demands for cleanliness and high processingprecision increase the need for reduced amounts of human interactionbetween the processing steps. This need has been partially met bytransport chambers, which operate as intermediate handling apparatusbetween such processing steps.

In the use of transport chambers, when a substrate is required forprocessing, a robot arm within the transport chamber may be used toretrieve a selected substrate from storage and place it into one of themultiple processing chambers. Transport of substrates among multiplestorage facilities and processing chambers is typically referred to ascluster tool architecture.

FIGS. 1A and 1B schematically illustrate a typical cluster toolarchitecture. substrates 101 may be stored in a clean room 102. Thesubstrates 101 may be the base on which layers are deposited insemiconductor processing, or by the material deposition systems, or maybe a support used in the flat panel display processing systems, forexample. Such substrates are very fragile, giving rise to a need tocarefully handle the substrates. The substrates 101 are commonlyreferred to as wafers.

A load lock 104 is generally coupled to the clean room 102. In additionto being a retrieving and serving mechanism, the load lock 104 alsoserves as a pressure varying interface between the clean room 102 and atransport chamber 106 that interfaces with various processing chambers108 a-108 c. FIG. 1B shows in more detail a cassette 110 in the cleanroom 102 for storing the substrates 101. The load lock 104 has a priorart end effector 112 within it. A drive assembly 114 serves to move anarm assembly 116 connected to the end effector 112. As described below,the prior art end effector 112 is made by alternately stacking prior artspatulas 118 and spacers 120. The load lock 104 also interfaces with thevarious processing chambers 108 a-108 c by way of a main robot arm 122of the transport chamber 106.

In use, the end effector 112 of the load lock 104 is moved through aport 124 of the clean room 102 and receives a supply of the wafers 101.In detail, each spatula 118 receives one of the wafers 101 from thecassette 110 and supports the wafer 101 for transport. The end effector112 is then moved out of the clean room 102 and back into the load lock104, where the wafers 101 are stored prior to being used for processing.Such processing is initiated by the main robot arm 122. reaching intothe load lock 104 and removing one of the wafers 101 from the supportedposition on the spatula 118.

It may be appreciated that two wafer transfer operations are required tomove the wafers 101 from the clean room 102 into a processing chamber108, and that each such transfer operation is to be accomplished withouthuman intervention. For the first transfer, the spatulas 118 of the endeffector 112 must be aligned with the wafers 101 contained in thecassette 110. If not aligned, horizontal movement of the end effector112 toward the cassette 110 may cause one or more of the spatulas 118 tomove horizontally and hit one or more of the wafers 101. Such hittingmay break the wafers 101, or otherwise damage the wafers 101, as byscratching an upper device surface 126, of the wafers 101. While thistype of damage to a wafer 101 is a significant cost factor in suchprocessing, a greater cost factor results when the end effector 112 isnot aligned with the main robot arm 122 in a second wafer transferoperation. For example, when the processing of the wafer 101 issubstantially complete, the value of the wafer 101 includes theincreased cost of the processing that has taken place since the wafer101 left the clean room 102. However, the first wafer transfer operationhas a greater potential of damaging multiple wafers, resulting in ahigher cost of production.

Attempts have been made to provide end effectors 112 with spatulas 118accurately aligned with both the cassette 110 (and the wafers 101therein) and the main robot arm 122. One such attempt is to make a stackof alternating spatulas 118 and spacers 120 as shown in FIG. 1C. There,bolts 132 are illustrated for squeezing the spatulas 118 and the spacers120 together to form the end effector 112. Referring to FIG. 1C, adesired relative positioning of the spatulas 118 is depicted byreference lines 128. This desired relative positioning will properlyalign each spatula 118 with the wafers 101 that are in the cassette andwith the robot arm 122 for transfer among the cassette 110, the loadlock 104, and the transport chamber 106. To achieve the desired relativespacing of the spatulas 118 of the end effector 112, attempts are madeto hold the thickness T of every one of the spacers 120 and every one ofthe spatulas 118 within a very close tolerance. For example, the samedesired relative positioning is indicated in FIG. 1D by the referencelines 128. However, the actual relative positioning (shown by referencelines 130 and 130U) differs significantly from the desired relativepositioning even though the spatulas 118 and the spacers 120 are withinthe desired tolerance (are in-tolerance). In this example, thesignificant difference is due to the thickness TT of spacers 120TT beingat the thick end of the tolerance. Such thicknesses TT are shown in FIG.1D accumulating, and resulting in and in-tolerance spacer 120 and thein-tolerance upper spatulas 118U being positioned above the referencelines 128 and 128U, indicating misalignment of the spatulas 118U. Suchmisalignment of the spatulas 118U with the reference lines 128 and 128Uresulting from the accumulation of tolerances is referred to astolerance stacking. Although not shown in FIG. 1D, such misalignment ofthe spatulas 118U with the reference lines 128 may also result from theaccumulation of tolerances that are at the thin end of the desiredtolerance. Tolerance stacking is a significant cause of the wafer damageproblem described above.

These misalignment problems not only cause the noted wafer damageproblems, but may also result in damage to the prior art end effectors118. Such end effector damage may require retooling of the prior art endeffector 118, such as by shutting down the operation of the load lock104, removing the prior art end effector 112 and replacing any brokenspatulas 118, for example.

It may be appreciated that the use of the stacked spatulas 118 and thespacers 120 for the prior art end effectors 112 is dependent on thesuccess of expensive efforts to make each of the spatulas 118 and eachof the spacers 120 within very tight tolerances, e.g. plus or minus0.0005 inches. Also, selection of spatulas 118 and spacers 120 for usein a particular end effector 112, and other costly steps necessary toattempt to reduce tolerance stacking in stacked arrangements of spatulas118 and spacers 120, give rise to an unfilled need to avoid using thestacked arrangements. Further, when these expensive manufacturingefforts fail, the noted significant cost factors (e.g., damage to anunprocessed wafer 101, or misalignment of the end effector 112, causingdamage to a wafer 101 that has been substantially completelymanufactured), are but a part of the resulting costs because processshut-down and reworking of the end effectors 112 may also be required tocorrect the end effector misalignment. Of course, any shut downsituation tends to reduce the yield or productivity of the processingand should be avoided.

In addition to these direct costs resulting from such misalignmentproblems, the risk of contamination is a factor in the prior art endeffectors 112 due to the multiple separate parts that are used to makesuch end effectors 112.

SUMMARY OF THE INVENTION

The present invention fills the need that is unfilled by the prior artend effectors by disclosing an end effector having a tower withnon-stacked spatulas, and a method of making the tower, the spatulas andthe end effector. In the described embodiments, the problem of tolerancestacking is avoided by making grooves in the tower relative to a commonreference surface, and mounting the spatulas in such grooves. Also, thegrooves are provided in separate walls of the tower. The walls areplanar and intersect to enhance the structural properties of the tower.The tower also has a dual-purpose clamp formed integrally with one wallfor use in assembling the tower and the spatulas, and for mounting thecompleted end effector in the load lock.

Advantageously, one embodiment of the present invention contemplatesusing the spatula for carrying a wafer during operations insemiconductor processing, or of material deposition systems, or in flatpanel display processing systems. The ability to carry the wafers isnotwithstanding vibration of equipment for performing the manufacturingoperations. The vibration of the equipment used in such processing orsystems is primarily in a range of frequencies. Each spatula is formedwith a planar platform having a mounting section and a wafer carryingsection. The wafer-carrying section has an aperture formed therein suchthat the platform carrying the wafer has a resonant frequency. In thisembodiment, the aperture is dimensioned so that the resonant frequencyof each unit (a spatula while carrying the wafer) is outside of therange of frequencies of the vibration of the equipment.

In another embodiment of the present invention, the wafer-carryingsection is provided with a plurality of holes around the aperture. Inconjunction with the holes, the spatula is provided with a pad forassembly with each of the holes. Each of the pads has a wafer supportsurface and a plurality of legs depending from the support surface. Eachof the legs has a distal end provided with a retainer edge and isflexible. The legs are flexed to permit the distal ends to be receivedin one of the holes. Upon receipt of the distal ends in the hole theretainer edges of the distal ends retain the pad in the hole with thesupport surface positioned to carry the wafer. The unit defined by theplatform with the pad carrying the wafer is provided with the resonantfrequency.

In a further embodiment of the present invention, there is provided amethod of making a tower for holding end effector components, such asthe spatulas. The components are to be accurately held relative to eachother, and the tower is provided with a column having a reference ledgethat defines a common reference surface. The method includes anoperation of forming a reference groove in the column, the referencegroove being dimensioned to receive one of the components and definingthe reference ledge at an accurate location above a base of the column.First and second additional grooves are formed in the column. The firstand second additional grooves are each dimensioned to receive anotherone of the components, and each defines a respective first and secondadditional ledge. In this embodiment, the operations of forming thefirst and second additional ledges are performed to provide the firstadditional ledge spaced by a selected distance from the common referencesurface defined by the reference ledge, and to provide the secondadditional ledge spaced from the common reference surface by a multipleof the selected distance. In this manner, the first and secondadditional ledges are evenly and accurately spaced from the commonreference surface and from each other, which is the desired relativespacing. These forming operations avoid the tolerance stacking problemsof the prior art end effectors since once the reference groove is madeto establish the reference ledge with the common reference surface, eachof the successive additional ledges is made with reference to the commonreference surface rather than with reference to the first additional orsecond additional or any successive previously made additional ledge.

Another aspect of the present invention is providing such method byforming a plurality of the first additional. grooves in the columnaccording to the performing operation, wherein the multiple of theselected distance is increased by one for each of the plurality of thefirst additional grooves.

Still another aspect of such method contemplates having each of thegrooves further define a staking section opposite to a respective one ofthe first and second ledges. Each groove has a given height to receiveone of the components. The method further includes the operation offabricating the column from material that is deformable by staking toreduce the given height of the grooves.

Yet another aspect of the present invention is a method of making an endeffector for holding piece parts, such as wafers, wherein the wafers areto be accurately held relative to each other. The end effector includesa tower and a spatula, the spatula having a first edge. The method isperformed by providing the tower with a plurality of grooves, each ofthe grooves defining a ledge and a staking portion opposite to theledge. After making a reference groove, respective ones of the nextledges are spaced from a common reference surface by a selected distanceand a different multiple of the selected distance to provide the nextgrooves and the next ledges without tolerance stacking. Also, the methodincludes inserting the first edge of the spatula into one of the grooveswith the spatula on the ledge of the one groove. Staking the stakingportion of the one groove is performed to hold the inserted first edgeof the spatula against the ledge of the one groove.

A further aspect of the present invention contemplates a method ofmaking an end effector for positioning wafers for processing, whereinthe wafers are to be accurately positioned relative to each other. Theend effector includes a tower and a plurality of spatulas. The methodcontemplates operations including making a reference groove to provide areference ledge that defines a common reference surface, and providing aplurality of the spatulas. The tower is provided with a plurality ofadditional grooves, each of the additional grooves defining anadditional ledge and a staking portion opposite to the additional ledge.Respective ones of the additional ledges are spaced from the commonreference surface by a selected distance and by different multiples ofthe selected distance to accurately and uniformly space the respectiveadditional grooves and ledges from the reference ledge without tolerancestacking.

Each of the grooves has a width dimensioned to loosely receive one ofthe spatulas. One of the spatulas is inserted into one of the grooveswith the one spatula on the ledge of the one groove. By staking thestaking portion of the groove to decrease the width of the one groove,the inserted spatula is held against the respective ledge. Then, theinserting and staking operations are repeated until all of the pluralityof spatulas have been held in successive ones of the grooves by therespective staked staking portions. The staking operation is performedat each of a plurality of spaced locations along the staking portion.

In another aspect of the present invention, the inserting and stakingoperations define a space between each of the respective spatulas andthe staking portion of a respective groove. The method further forcesbrazing filler into each of the spaces between each of the spatulas andthe staking portions of the respective grooves. Another operationprovides each of the spatulas with a free edge opposite to a respectivegroove. A plurality of brazing fixtures are provided with a plurality ofslots, each of the slots defining an edge support. Respective ones ofthe edge supports are spaced from the common reference surface by theselected distance and by a different multiple of the selected distanceto provide the slots and the edge supports without tolerance stacking.Upon completing all of the operations to insert the spatulas into thegrooves, each respective free edge of the spatulas is inserted into arespective slot, and a spring clip is inserted into the respective slotto urge the spatula against the respective edge support. A fixtured endeffector results from this method.

To complete the end effector, the present invention contemplatesgradually preheating the fixtured end effector and dip brazing theheated fixtured end effector to secure the spatulas to the tower withouttolerance stacking.

These and other advantages of the present invention will become apparentupon reading the following detailed descriptions and studying thevarious figures of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings.

FIG. 1A is a diagrammatic illustration of a typical prior art clustertool architecture which illustrates how various processing chambers maybe coupled to a transport chamber which operates with a load lock whichreceives wafers from a clean room.

FIG. 1B is an elevational view of a portion of the cluster toolarchitecture illustrating the load lock transporting a supply of wafersreceived from a cassette in the clean room for delivery to the transportchamber.

FIG. 1C is an enlarged elevational view of a prior art end effectorillustrating a stack of spacers and spatulas held assembled by bolts.

FIG. 1D is an enlarged elevational view of the prior art end effectorshown in FIG. 1C illustrating the stack of spacers and spatulas in anundesirable tolerance stacking situation.

FIG. 2A is a plan view of a spatula of the present inventionillustrating edges positioned relative to each other at a given angle,holes for receiving wafers pads, and an aperture dimensioned forproviding a selected resonant frequency.

FIG. 2B is a three dimensional view of a unit including a spatula, waferpads, and a wafer on the pads.

FIGS. 3A and 3B are views of the wafer pad shown in FIG. 2B,illustrating legs for retaining the pads to the spatula, and in FIG. 3Billustrating the holes for receiving the wafers pads.

FIG. 4A is a three-dimensional view of a tower of the present invention,illustrating grooves formed in one of two walls for receiving thespatulas.

FIG. 4B is a plan view of the tower showing walls positioned relative toeach other at an angle substantially the same as the given angle, and aclamp integral with one of the walls.

FIG. 4C is an elevational view of the tower illustrating how a referencegroove is formed in the tower to define a common reference surface, andhow each of a plurality of additional grooves is formed in the wallsrelative to the common reference surface to avoid tolerance stacking.

FIG. 5A is a plan view of the end effector of the present inventionillustrating the tower assembled with one of the spatulas and a wafersupported on the spatula.

FIG. 5B is an enlargement of a portion of the end effector shown in FIG.5A, illustrating the locations at which a staking operation is performedto secure a spatula to the walls of the tower.

FIG. 5C is an enlarged elevational view illustrating a spatula receivedin one of the grooves and resting on a ledge, where a space isillustrated between the upper surface of the spatula and the upperportion of the groove prior to the staking operation.

FIG. 5D is a view similar to FIG. 5C after the staking operation hasbeen performed, illustrating deformation of a staking portion intocontact with the upper surface of the spatula to hold the spatulaagainst the ledge.

FIG. 5E is a three-dimensional view of the end effector shown in FIG.5A, illustrating a plurality of spatulas secured to the tower andwelding fixtures removably attached to the spatulas for holding thespatulas in position during brazing.

FIG. 5F is an elevational view illustrating fixturing of the endeffector using a plurality of combs.

FIG. 5G is an enlarged view of a portion of FIG. 5F illustrating springclips used in the fixturing with the comb.

FIG. 6 is a three dimensional view of the assembled end effector,illustrating the tower secured to the plurality of spatulas.

FIG. 7A is a flow chart showing the operations of one embodiment of amethod of the present invention for manufacturing the tower with groovesto avoid tolerance stacking.

FIG. 7B is a flow chart illustrating the operations of anotherembodiment of a method of the present invention where a plurality ofspatulas are positioned without tolerance stacking and the spatulas aresecured to the tower by staking operations.

FIG. 7C is a flow chart illustrating the operations in the assembly ofthe end effector of the present invention by joining the tower withspatulas, wherein heating and brazing operations follow joining thespatulas to the tower by the staking operations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As described above, FIGS. 1C and 1D illustrate the problem of tolerancestacking, in which there are significant differences between the desiredrelative positioning of exemplary prior art spatulas 118 (indicated byreference lines 128 and 128U), and actual relative positioning of theexemplary prior art spacers 120TT (indicated by reference lines 130 inFIG. 1D). In the example, the significant differences are due to thethicknesses TT of spacers 120TT being at the thick end of the desiredtolerance. Such thicknesses TT are shown in FIG. 1D as accumulating, andresulting in the actual positioning (indicated by reference lines 130and 130U) of upper spatulas 118U above the reference lines 128 and 128U.The actual positioning indicates misalignment of the spatulas 118U, asdescribed above. It was noted that such misalignment of the spatulas118U with the reference lines 128 may also result from the accumulationof tolerances that are at the thin end of the desired tolerance.

An invention is described below for improving the efficiency ofmanufacture of end effectors 200 (FIG. 6), and of components of such endeffectors (e.g., spatulas 202), through the implementation of ways ofmaking grooves 204 in a tower 206 relative to a common reference surface208 (FIGS. 2A and 4A). In the following description, numerous specificdetails are set forth in order to provide a thorough understanding ofthe present invention. It will be obvious, however, to one skilled inthe art, that the present invention may be practiced without some or allof these specific details. In other instances, well known manufacturingoperations have not been described in detail in order not to obscure thepresent invention.

FIG. 2A is a plan view of a single spatula 202 manufactured according toone embodiment of the present invention. The spatula 202 carries a piecepart, such as a wafer, 210 (FIG. 2B), during semiconductor processingoperations, or in the operation of material deposition systems or offlat panel display processing systems. The spatula 202 is machined fromaluminum plate, for example, by a fine blanking technique well known tothose skilled in the art. This technique defines a perimeter 212 havingan edge 214 formed in many sections 216. A first section 216A of theedge 214 is shown intersecting a second section 216B at an angle 218.The angle 218 may, for example, be a right angle. Other sections 216Cand 216D of the edge 214 extend away from the intersecting respectivefirst and second sections 216A and 216B, and with the respective firstand second sections 216A and 216B, define a mounting portion 220 of thespatula 202. The mounting portion 220 has an upper surface 222. Spacedsections 216E and 216F extend away from the mounting portion 220. Adistal edge section 216G extends around a distal end 224. The sections216E, 216F, and 216G define a portion 226 of the spatula 202 forcarrying one of the wafers 210. To minimize the area of a wafer 210 thatis touched during such carrying, holes 228 are provided at spacedlocations, such as at points defined by center lines 230A, 230B, and230C. Also, an aperture 232 is formed in the carrying portion 226 withinan area defined by the holes 228. The aperture 232 has a diametercentered on an aperture axis 234, and each of the holes 228 has adiameter centered on a hole axis 236.

FIGS. 3A and 3B illustrate a pad 238 provided for assembly with each ofthe holes 228. Each of the pads 238 has a wafer support surface 240 anda plurality of legs 242 depending from the support surface 240 parallelto a leg axis 244. The wafer support surfaces 240 of the threeillustrated pads 238 cooperate to provide the minimum area of the wafer210 that is touched during the carrying of the wafer 210. To secure thepad 238 to the spatula 202, distal ends 256 are positioned within theholes 228 such that surfaces 252 are caused to contract in a direction250 while placing a holding/friction force against the inner surface ofthe holes 228. To assist in inserting the pads 238 into each of theholes 228, the distal ends 256 have bevels 258. The distal ends 256 alsohave bottom surfaces 260 which are preferably contained within the holes228 and above the level of surface 266 of the spatula 202.

In the manufacture of one embodiment of the spatula 202 of the presentinvention, the following is recognized. Vibrations are created duringsemiconductor processing operations, or in the operation of materialdeposition systems or of flat panel display processing systems, theequipment (not shown) used for such operations or in such systems. Thevibrations of the equipment are primarily in a range of frequencies,such as 35 cps to 37 cps. In such manufacture it is also recognized thata vibration unit 268 is formed by one of the spatulas 202, the threepads 238, and one of the wafers 210 carried by the three pads 238. Sucha unit 268 is shown in FIG. 2B, and it is further recognized that theunit 268 will have a resonant frequency. The spatula 202, and theassociated pads 238, must nonetheless carry the wafer 210 in such amanner that any vibration of the unit 268 will not cause the wafer 210to move in response to the vibrations (e.g., walk) off the pads 238. Toachieve this result, once the range of frequencies of such equipment isknown, the aperture 232 is dimensioned so that the resonant frequency ofsuch unit 268 will be out of this range. In this manner, the amplitudeof the vibration of the unit 268 will be reduced, which tends to avoidwalking of the wafers 210 off the pads 238. The dimensioning of theaperture 232 may, for example, use a selected diameter for a circularaperture 232, or the aperture 232 may have any other non-circular shapedesigned to achieve the desired resonant frequency of the unit 268. Fordetermining the resonant frequency, in one embodiment, an accelerometercan be mounted on spatula 202, tapping the spatula, and recording thesignal from the accelerometer. In this manner, the proper size and shapeof aperture 232 can be predicted using finite element analysis. Once theshape and size of the aperture 232 have been selected, one of thespatulas 202 is formed with that shape and size aperture 232, and thepads 238 are assembled with the spatula 202. The unit 268, with atypical wafer 210 on the three pads 238, is mounted to a tower 206 inthe manner described below. The tower 206 is mounted to a vibrationtable (not shown). The table vibrates the tower 206 and the unit 268 todetermine that the resonant frequency of the unit 268 is out of thisrange. The shape and size of the aperture 232 may be adjusted asnecessary to achieve the desired resonant frequency of the unit 268,which is outside of the range of vibration of the equipment.

In one embodiment of the spatula 202, the spatula 202 may be fabricatedfrom plate aluminum, such as that meeting the standard 6061-T4specification, for example, such that the spatula 202 is planar. Suchplate aluminum may, for example, have a thickness of about 0.150 inchesplus or minus 0.001 inch. Further, the carrying portion 226 may bestress relieved prior to final machining. In such embodiment, exemplarydimensions of the spatula 202 include an overall length of about eleveninches, a length of the carrying portion 226 of about 7.6 inches, and awidth of the mounting portion 220 of from about 3.1 inches to about 1.6inches. Radii of the sections 216C and 216P having curved portions mayinclude a radius R1 of about 1.5 inches, and a radius R2 of about 0.75inches; whereas a proximal end 270 may have a radius R3 of about 1.0inch. Corners 272 of the spatula 202 may, for example, be arcuate havinga radius R4 of about 0.3 inches. Also, the holes 228A and 228B may belocated about 0.3 inches from the distal end 224. The hole 228A may belocated about 0.3 inches from the section 216F, and the hole 228B may belocated about 4.3 inches from the section 216F. The third hole 228C maybe located about 6.06 inches from the distal end 224, whereas theaperture 232 may be about 1.46 inches from the distal end 224. The thirdhole 228C may be aligned with the aperture 232 at about 2.3 inches fromthe section 216F.

FIG. 4A illustrates the three-dimensional aspects of the tower 206 ofthe present invention, showing the tower 206 in a vertical position forholding components, such as the spatulas 202 shown in FIGS. 2A and 2B.The tower 206 holds the spatulas 202 accurately relative to each other,which is in the desired relative positions described above. The tower206 may include a column 274, or other vertical member, having aplurality of the grooves 204 formed therein. Each of the grooves 204 isdimensioned to receive one of the spatulas 202 and defines a ledge 276.Thus, the plurality of grooves 204 define a plurality of ledges 276along the column 274. The column 274 has a base 278 provided with asurface, referred to as an initial reference surface 280, which definesthe location of a common reference groove 204R. The common referencegroove 204R has a reference ledge 276R which defines a common referencesurface 282 from which the desired relative positioning of additionalones of the grooves 204A described above is determined.

FIG. 4B is a plan view of the column 274 shown in FIG. 4A, illustratingthe column 274 including first and second walls 284C and 284F,respectively, which extend at a selected angle 286 relative to eachother. For example, the selected angle 286 of the walls 284C and 284Fmay be a right angle relative to each other, and such angle 286 shouldcorrespond to the angle 218 at which the first and second sections 216Aand 216B of the edge 214 of the spatula 202 are positioned relative toeach other. It may be understood that for spatulas 202 having first andsecond sections 216A and 216B positioned at a different angle 218relative to each other, the walls 284C and 284F of the column 274 willbe at a selected angle 286 corresponding to that different angle 218.

The walls 284C and 284F are shown having flat opposite sides such thateach of the walls 284C and 284F is planar. The second wall 284C of thewalls 284 is shown formed integrally with a device 288 for holding thetower 206 to a post 290 (FIG. 5E) or other support which may be providedin the manufacture or use of the end effector 200. The device 288 may bereferred to as a clamp in that a cylindrical portion 292 of the device288 is connected to the wall 284C and extends circularly to an opening294. The opening 294 defines opposed flanges 296 of the cylindricalportion 292. There is a gap 298 between the opposed flanges 296 to allowthe diameter 300 of the cylindrical portion 292 to be adjusted. Forexample, with the gap 298 wide, the cylindrical portion 292 may beplaced, on the post 290. Then, the gap 298 may be made smaller bydrawing the flanges 296 closer to each other. Holes 302 are provided inthe flanges 296 and fasteners 304 are inserted in the holes 302 totighten the flanges 296 on the post 290 to secure the column 274 in adesired place. The first wall 284F is thus free in that it is spacedfrom the clamp 288. However, because of the selected angle 286 betweenthe walls 284F and 284C, when the clamp 288 is secured to the post 290,both walls 284C and 284F remain in a stable vertical position forholding the spatulas 202 accurately and horizontally.

FIG. 4C is an elevational view of the column 274 showing the grooves 204formed in the walls 284C and 284F. With the walls 284C and 284Fintersecting along a line 306 (shown as vertical in FIGS. 4A and 4C), itis to be understood that each particular one of the grooves 204 extendshorizontally across the line 306 so that each groove 204 extendscontinuously along the complete extent of the respective first andsecond walls 284F and 284C.

Each one of the grooves 204 defines one of the ledges 276, and a stakingportion 308 opposite to the ledge 276. There is a space 310 defined byeach of the grooves 204, an under surface 312 of each staking portion308, and an inner end 314 of each groove 204. The space 310 has adimension S large enough to receive the thickness of one of the spatulas202. FIG. 4C also shows the initial reference surface 280 defined by thebase 278. The walls 284F and 284C and the clamp 288 extend verticallyupwardly from the initial reference surface 280.

One embodiment of a method of the present invention relates to makingthe tower 206 for holding the components (e.g., the spatulas 202) of theend effector 200, wherein the spatulas 202 are to be accurately heldrelative to each other. This embodiment is described in FIG. 7A.Referring to FIG. 7A, this embodiment of the method includes anoperation M501 of forming the initial reference groove 204R in the walls284. The initial reference groove 204R is made by measuring from theinitial reference surface 280 a distance equal to the thickness (orheight) of the base 278. At that distance, the reference groove 204R isformed, as by grinding, for example. The reference groove 204R definesthe ledge 276, which is referred to as the common reference ledge 276R.The common reference ledge 276R provides the common reference surface282 for making additional ones of the grooves 204A and their respectiveadditional ledges 276A.

Still referring to FIG. 7A, this embodiment of the method includes afurther operation M502 of forming a first additional groove 204 in thewalls 284. The first additional groove 204 is dimensioned to receiveanother one of the spatulas 202 and defines a first additional ledge276A1. As shown in FIG. 4C, the distance from the common referencesurface 282 to any one of the additional ledges 276A is either aspecified amount, referred to as D (e.g., for the first additional ledge276A1), or a multiple of D (e.g., for the remainder of the additionalledges 276A).

Still referring to FIG. 7A, this embodiment of the method includes afurther operation M503 of forming a second additional groove 204A2 inthe walls 284. The second additional groove 204A2 is also dimensioned toreceive another one of the spatulas 202 and defines a second additionalledge 276A2.

It may be understood that this embodiment of the method includesperforming each of the additional groove forming operations M502 andM503 to provide the first additional ledge 276A1 spaced by the selecteddistance D from the common reference surface 282 and to provide thesecond additional ledge 276A2 spaced from the common reference surface282 by a multiple of the selected distance D. As a result, the firstadditional ledge 276A1 and the second additional ledge 276A2 are evenlyand accurately spaced from the common reference surface 282 and fromeach other.

This embodiment of the method may be continued by performing anoperation M504 of forming a plurality of the second additional grooves204A in the walls 284 as described above (e.g., additional grooves 204A3to 204AN, where N exceeds 3). In this situation, the multiple of theselected distance D is increased by one for each of the plurality ofsecond additional grooves 204A.

In more detail, and still referring to FIG. 4C, this embodiment of themethod provides the first additional ledge 276A1 of the additionalledges 276A spaced by the selected distance D from the common referencesurface 282 defined by the reference ledge 276R. Also, a plurality ofthe successive additional ledges 276A2 through 276A12 are, for example,shown spaced from the common reference surface 282 by a uniformlyincreasing multiple of the selected distance D. In this manner, theplurality of additional ledges 276A2 through 276A12 are evenly andaccurately spaced from the common reference surface 282 at which thereference ledge 276R is located, and from each other. The amount of theuniformly increasing multiple of the selected distance D may be 1, forexample, so that the distance of the first additional ledge 276A1 fromthe common reference surface 282 is D, and the distance of the secondadditional ledge A2 from the common reference surface is 2 times D, andthe distance of the third additional ledge 276A3 from the commonreference surface 282 is 3 times D, and the distance of the ledge 276A12from the common reference surface 282 is 12 times D, for example.

The number of grooves 204 to be provided in any particular wall 284depends on the number of spatulas 202 which need to be used to carry allof the wafers 210 contained in any given one of the cassettes 110. Inone embodiment of the present invention, up to twenty-five grooves 204may be provided in the walls 284. It may be appreciated that theadvantages of the present invention become more significant withincreases in the number of wafers 210 to be carried. In more detail,because there is no tolerance stacking of the additional ledges 276Aformed in the walls 284, only one tolerance is involved between anygiven additional ledge 276A and the common reference surface 282. Incontrast, as is clear from the above description of

FIG. 1D, with each increase in the number of wafers 210 to be carried bythe prior art end effectors 112, each prior art spacer 120 and eachprior art spatula 118 presents another opportunity for introducing anincrease in the amount of error in the actual relative positioning ofthe spatulas 118 as compared to the desired relative positioning.

In one embodiment of the tower 206, the tower 206 may be fabricated from6061-T4 aluminum alloy. Such aluminum alloy may have a thickness ofabout 0.25 inches. Further, the tower 206 may be stress relieved priorto final machining. In such embodiment, exemplary dimensions of thetower 206 include the following. There may be provided an overall heightof about 5.3 inches, a length of the wall 284C of about 3.5 inches, alength of the wall 284F of about 1.8 inches, and a distance of about0.975 inches from the outside of the wall 284C to the centerline 316 ofthe clamp 288. The clamp 288 may be about four inches high, for example.The diameter of an outer wall 318 of the clamp 288 may be 0.875 inches,and the diameter of an inner wall 320 of the clamp 288 may be 0.625inches, for example. The centerline 316 of the clamp 288 may be about3.65 inches from the wall 284F. The grooves 204 may be 0.125 inches deep(perpendicular to the plane of a wall 284) for example. The height ofeach of the grooves 204 may be 0.153 inches plus or minus 0.001 inch. Inthis manner, the spatulas 202 having the above identified exemplarythicknesses of about 0.150 inches may be received in the grooves 204.

The common reference ledge 276R may be spaced from the initial referencesurface 280 by 0.25 inches plus or minus 0.001 inch. The distance D fromthe common reference ledge 276R to the first additional ledge 276A1 maybe 0.3937 inches plus or minus 0.0020 inches. As described above, thedistance from the common reference ledge 276R to the second additionalledge 276A2 may be 2 times 0.3937 inches (or 0.6874 inches) plus orminus 0.0020 inches. Thus, 2 is the multiple. As described above, thereis a uniform increase in the value of the multiple from one additionalledge 276A to another additional ledge 276A. For example, the thirdadditional ledge 276A3 is made with reference to 3 times 0.3937 inches(plus or minus 0.0020 inches) measured from the common reference surface282 defined by the reference ledge 276R. Similarly, the fourthadditional ledge 276A4 is made with reference to 4 times 0.3937 inches(plus or minus 0.0020 inches) measured from the common reference surface282 defined by the common reference ledge 276R. It may be understoodthen that if there are N additional grooves 204, the Nth additionalgroove 204 will be made with reference to N times 0.3937 inches (plus orminus 0.0020 inches) measured from the common reference surface 282.

FIG. 5A is a plan view of the end effector 200 of the present inventionillustrating the tower 206 assembled with one of the spatulas 202. Forillustration purposes, the center of a wafer 210 is shown beingconcentric with the center of aperture 232. Although any size or shapesubstrate may be carried by the spatulas of the end effector 200,preferably circular-type wafers, such as a 300 mm (11.811 inch) wafer iscarried by each of the spatulas 202. The first and second sections 216Aand 216 b of the edge 214 of the spatula 202 are shown conforming to theshape of the inner ends 314 (FIG. 5A) of the grooves 204. FIG. 5B showsan enlargement of a portion of the assembled tower 206 and the spatula202 and illustrates a plurality of locations (each indicated by a shortline 322) at which a staking operation is performed. FIG. 5C is a crosssection illustrating the process of assembly of the tower 206 with aspatula 202. The spatula 202 is illustrated in the groove 204. FIG. 5Dshows the result of performing the staking operation to secure thespatula 202 in one of the grooves 204. FIG. 5C illustrates one of thethree locations 322 (shown in FIG. 5B) as having the staking operationperformed. It may be understood that the one embodiment of the method ofthe present invention may include an initial additional operation M500of fabricating the column 274 from material that is deformable bystaking to reduce the height 324 of the space 310 of the grooves 204.This operation M500 is achieved by using the plate aluminum for thetower 206 as described above.

Referring again to FIG. 5C, one of the grooves 204 is shown defining thestaking portion 308, which is above the ledge 276 of the groove 204.Because of the height 324 of the space 310 of the groove 204, prior toperforming a staking operation, there is the space 326 between the uppersurface 222 of the spatula 202 and the under surface 312 of the groove204. FIG. 5D is similar to FIG. 5C, but differs in that FIG. 5Dillustrates the staking portion 308 after the staking operation has beenperformed by using a staking tool 328. The staking tool 328 shown inFIG. 5D is used to deform the staking portion 308 to define a tab 330that is formed to press (as viewed in FIG. 5D) against the upper surface222 of the spatula 202 that is in the groove 204. The tab 330 urges thespatula 202 down (as viewed in FIG. 5D) against the ledge 276. Thestrength of the staking portion 308 is such that the tab 330 remains inthe position shown in FIG. 5D so as to hold the spatula 202 against theledge 276.

Referring to FIGS. 4B, 5C, 5D, 5E and 7B, another embodiment of themethod of the present is illustrated. An operation M520 is for providingthe tower 206 with a plurality of the grooves 204. Each of the grooves204 defines one of the ledges 276 and the staking portion 308 oppositeto the ledge 276. Respective ones of the ledges 276 are spaced from thecommon reference surface 282 by the selected distance D, for example,and a multiple of the selected distance D to provide the grooves 204 andthe ledges 276 without tolerance stacking. An operation M521 is forinserting the first edge 334 of the spatula 202 into one of the grooves204 with the spatula 202 on the ledge 276 of the one groove 204. Anoperation M522 is for staking the staking portion 308 of the one groove204 to hold the inserted first edge 334 of the spatula 202 against theledge 276 of the one groove 204.

Further operations may be taken to complete the tower 206, as by thefollowing. The insertion operation M521 may be performed one-by-onestarting from the bottom of the base 278 and first inserting a spatula202 in the reference groove 204R. One of the tabs 330 shown in FIG. 5Dis formed. Then, the next upward spatula 202 is inserted into the nextupward groove 204, which defines the first additional ledge 276A1.Another one of the tabs 330 shown in FIG. 5D is formed. This series ofinsertion operation M521 and staking operation M522 may be repeateduntil all of the spatulas 202 have been inserted into all of the grooves204 and all of the staking portions 308 have been staked.

FIG. 7C describes another embodiment of a method of the presentinvention. In an operation M530, pre-cleaning of all of the componentsof the end effector 200 and of the parts for brazing (e.g., the brazingfixture 346 and the clips 354 is performed. The pre-cleaning is in anacid solution. Then such components and parts are rinsed in water. Then,an operation M531 may be performed to mount a spatula 202 to a tower 206one-at-a-time. Each spatula 202 is staked to the tower 206.

Having inserted all the spatulas 202 into all of the grooves 204, andhaving staked all of the staking portions 308, it may be understood thatexcept at the locations 322 at which the staking operation has beenperformed, the grooves 204 that have received the spatulas 202 stillhave the space 326 between the under surface 312 and the upper surface222 of the spatula 202 as shown in FIG. 5C.

M532 is the next operation of this embodiment of the method of thepresent invention, in which a dip brazing filler 336 (FIG. 5C) isapplied into each of the spaces 326 between the upper surfaces 222 andthe under surfaces 312. To apply the brazing filler 336, the filler 336is provided in an injector 338, which may be syringe-like having a longhollow needle 340. As described in FIG. 7C, and with reference to FIG.5E, the needle 340 is inserted into a space 342 between one pair 344 ofthe spatulas 202. The needle 340 extends to the space 326 shown in FIG.5C. The injector is then operated to discharge the brazing filler 336into the space 326 along the entire extent of one of the grooves 204.This process is repeated with the next space 342 between the next pair344 of spatulas 202 until all of the spaces 326 in all of the grooves204 have been filled with the brazing filler 336.

At this juncture, the tower 206 is in the condition shown in FIG. 5F,except for four brazing fixtures (or combs) 346 that are shown in FIG.5F. In detail, the mounting portion 220 of each of the spatulas 202 isheld in place in the respective groove 204 by the three tabs 330 (FIG.5B), such that the carrying portion 226 is cantilevered from themounting portion 220. Also, the brazing filler 336 is in all of thespaces 326.

FIG. 5E illustrates the four brazing fixtures 346, with three shownlocated adjacent to the carrying portion 226 and one located adjacent tothe mounting portion 220. Referring to FIG. 5F, each of the brazingfixtures 346 is provided with a plurality of slots 348. Each of theslots 348 defines an edge support 350 on which one of the spatulas 202rests. The slots 348 are formed in the brazing fixtures 346 in the samemanner as the grooves 204 are formed. As a result, after a referenceslot 348R is formed and defines a common fixture reference surface 352,additional slots 348 are formed so that respective ones of the edgesupports 350 are spaced from the common fixture reference surface 352 bythe same selected distance D and the same uniformly increased multipleof the selected distance D to provide the slots 348 and the edgesupports 350 without tolerance stacking.

In an operation M533, the brazing fixtures (or combs 346) are used tofixture the tower 206, which is by applying the combs 346 to hold thespatulas 202 in place. The fixturing supports the carrying portion 226and the mounting portion 220 of the each of the spatulas 202 for abrazing operation. For this purpose, operation M533 may includepositioning the brazing fixtures as shown in FIG. 5E adjacent to therespective carrying portion 226 and to the mounting portion 220.Operation M533 may also include inserting the edges of these carryingportions 226 and mounting portions 220 of all of the spatulas 202 into arespective one of the slots 348 of the comb 346.

FIGS. 5F and 5G illustrate a final aspect of operation M533 of thisfixturing, which is to insert a spring clip 354 into a space 356 betweenthe upper surface 222 of the spatula and an under surface 358 of theslot 348 of the comb 346. The clip 354 is a U-shaped resilient memberhaving legs 360 self-biased apart. As shown in the enlarged FIG. 5G, thelegs 360 of the clip 354 has been pressed together as it was insertedinto the space 356, which holds the spatulas 202 in the slots 348. Theresult of this fixturing process is referred to as a fixtured endeffector 362, and is as shown in FIG. 5E.

The fixtured end effector 362 is then processed in a further operationM534, in which there is gradual pre-heating of the fixtured end effector362. The preheating operation M534 is a standard operation in dipbrazing, such that one skilled in the art will understand that thepre-heating is typically performed in an oven (not shown) to increasethe temperature of the fixtured end effector 362 to 1000 degrees F. Asfurther illustrated in FIG. 7C, as operation M535, in a standard mannerthe pre-heated fixtured end effector 362 is then immersed in a moltenlithium bath (not shown) having a temperature of 1100 degrees F. toactivate the brazing filler 336. In the immersion, the aluminum materialfrom which the end effector 200 is fabricated changes from a T4condition to a T0 condition and becomes softer. In another operationM536 illustrated in FIG. 7C, the brazed end effector 200 is cooled inair at room temperature for about twelve hours. In an operation M537 thecombs 346 and the clips 354 are removed from the cool end effector 200.In a final operation M538, the end effector 200 is cleaned in a standardpost-brazing operation by using an acid solution and a final waterrinse.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. In addition, although the preferred materials used tomake the end effector 200 is plate aluminum and stainless steel asdescribed above, any other suitable material, such as steel, etc., maybe substituted therefor. Therefore, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalence of the appended claims.

What is claimed is:
 1. A tower for holding components of an endeffector, wherein the components are to be accurately held relative toeach other, the tower comprising: column having a plurality of groovesformed therein, each of the grooves being dimensioned to receive one ofthe components and defining a ledge so that the plurality of groovesdefine a plurality of ledges along the column; the column having a baseprovided with a reference ledge to define a reference surface; a firstof additional ledges being spaced by a selected distance from thereference surface; successive ones of the additional ledges being spacedfrom the reference surface by a uniformly increasing multiple of theselected distance so that the plurality of additional ledges are evenlyand accurately spaced from the reference surface; wherein the componentsare spatulas for holding wafers for semiconductor processing, thespatulas having edges that intersect at a given angle, the tower furtherhaving, the column being formed from a plurality of walls, wherein eachof the walls extends away from the reference surface and issubstantially planar; and the walls intersecting to define anintersection at a tower angle substantially the same as the given angle.2. A tower according to claim 1, wherein: the intersection of the wallsis along a first line; and each of the grooves extends across the firstline so that each groove and each respective ledge of the groove extendscontinuously along the plurality of walls.
 3. A tower according to claim1, the tower further comprising: a hollow cylinder formed integrallywith the column; and the cylinder having a split portion defining a pairof opposed spaced flanges for clamping the tower in position to hold thecomponents.
 4. A tower according to claim 3, wherein: the flanges areprovided with at least one pair of opposed holes; and fasteners extendthrough the at least one pair of the opposed holes for urging theflanges together to clamp the tower in the component holding position.5. A tower for holding components of an end effector, comprising: a basesurface; a vertical member having a plurality of grooves; and aplurality of ledges being defined by the grooves, the plurality ofledges being configured to hold the components of the end effector,wherein the ledges are spaced the multiple of the selected distance fromthe base surface, wherein the components are spatulas for mountingwafers, the spatulas having edges that intersect at a given angle,further including, a plurality of walls extending from the base surface,wherein the walls are substantially planar and the grooves and theledges are formed on the walls; and the walls intersect to define anintersection at a tower angle such that the tower angle is substantiallythe same as the given angle.
 6. A tower for holding components of an endeffector as recited in claim 5, wherein the grooves and the ledges areformed at the intersection of the walls such that the grooves and theledges are continuous along the walls and the intersection.
 7. A towerfor holding components of an end effector as recited in claim 5, furthercomprising: a column formed from the plurality of walls, wherein thecolumn has a hollow cylinder integrally formed with the column; and thehollow cylinder having a split portion defining a pair of opposed spacedflanges for clamping the tower in position to hold the components.
 8. Atower for holding components of an end effector as recited in claim 7,wherein the opposed spaced flanges have at least one pair of opposedholes such that fasteners extend through the at least one pair of holesfor urging the opposed space flanges together to clamp the tower in theposition to hold the components.
 9. A tower for holding components of anend effector, comprising: a base surface; a vertical member extendingfrom the base surface; a plurality of grooves defined in the verticalmember, each groove having a ledge that is a multiple of a distance fromthe base surface, wherein the grooves are dimensioned such that thegrooves can receive the components of the end effector and the groovecan accurately hold the components relative to each other, the verticalmember defines a plurality of walls such that the walls define thegrooves and the ledges; a column formed from the plurality of walls,wherein the column has a hollow cylinder integrally formed with thecolumn; and the hollow cylinder having a split portion defining a pairof opposed spaced flanges for clamping the tower in position to hold thecomponents.
 10. A tower for holding components of an end effector asrecited in claim 9, the opposed spaced flanges have at least one pair ofopposed holes such that fasteners extend through the at least one pairof holes for urging the opposed space flanges together to clamp thetower in the position to hold the components.